KR102054541B1 - In-tool esd events monitoring method and apparatus - Google Patents

Abstract

In one embodiment of the present invention, an apparatus for monitoring an electrostatic discharge (ESD) event incorporating a charged device model event simulator (CDMES) unit comprises: at least one antenna positioned within a process area; And an ESD detector coupled to the at least one antenna, wherein the ESD detector is wirelessly coupled to the CDMES unit, and the ESD detector is calibrated for different discharge energy generated by the CDMES unit.

Description

Method and apparatus for monitoring ESD event in tool {IN-TOOL ESD EVENTS MONITORING METHOD AND APPARATUS}

CROSS REFERENCE TO RELATED APPLICATIONS

This application claims priority to US Provisional Application No. 61 / 747,199.

<Technology field>

Embodiments of the present invention generally include methods and apparatus for in-tool monitoring and characterization of electrostatic discharge (ESD) events, and / or charged device model event simulators; CDMES) / minipulse (Mini apparatus and method, and / or other types of CDMES, detectors and methods. At least one method and apparatus disclosed herein is, for example, integrated circuit (IC) production. Provide real-time ESD event monitoring in tools and / or different processes and assist in suppressing ESD related filters using one or more method (s) of a charged device model (CDM). Two methods for calibrating the method and monitor are disclosed herein.

The background description presented herein is generally for illustrating the context of the present disclosure. Although the work of the presently-discussed inventors is described in this background section, aspects of this achievement and descriptions that would otherwise not qualify as prior art at the time of application are expressly or as prior art to this disclosure. It is not implicitly acknowledged.

CDM events represent electrostatic discharges that occur in manual and automated production systems for electronic ICs. In a production tool, an IC can acquire charges in a number of ways, such as, for example, contact, friction, and / or induction from near magnetic fields, to mention only a few possible ways. When the conductive parts of the ICs come in contact with grounded equipment parts or parts with lower potential, the accumulated IC charges will spontaneously free discharge. As a result, a relatively high discharge current (ESD event) can destroy or damage the IC (see, eg, FIGS. 1A and 1B).

The design of IC components usually includes special means of protection (or specific components) to prevent ESD effects. The semiconductor industry has developed several standard methods for testing IC devices and defined CDM ESD threshold parameters such as, for example, withstand voltage and current amplitude. Applicable standards also enumerate test device requirements for automated IC CDM testing. These methods and devices are useful in IC design stages, final testing for product assurance, and failure analysis of compromised devices.

However, the prior art is subject to various limitations and / or deficiencies as will be discussed below. It is an object of various embodiments of the present invention to provide a method and apparatus for real-time ESD event monitoring and calibration in IC production tools and manufacturing processes.

1A illustrates a typical discharge model 100 of a charged (IC) device CDM event in a tool or processing chamber. In FIG. 1A, a MiniPulse ESD detector 105 (or another type of ESD detector 105) intercepts an electromagnetic wave 140 and a Robot Placement Effector 115 (or other suitable type). Robot arm 115 places charging device 125 in test socket 130. Test socket 130 is typically disposed on a suitable test bed 131, base 131 or other suitable platform 131. When the charging device 125 approaches the test socket 130, an discharge (ESD) occurs, and antenna 135 (coupled to the minipulse detector 105) intercepts the electromagnetic wave 140 of the discharge event. do. In this example, the ESD event is a discharge 141 that occurs in the form of a spark between two conductive parts 125 and 130 with different potentials. Conductive components 125 and 130 and other semiconductor processing equipment may be in tool or processing chamber 132, which may have any suitable size, such as, for example, approximately 2x2 feet, 4x4 feet or other dimensions. .

The current problem with the prior art is the difficulty in calibrating the ESD detector. This difficulty is due, for example, to the challenges in providing repeatability of the discharge event itself. Other difficulties also exist due to the configuration of the process point itself and the conditions imposed on the electric field waveform emitted by the materials. Therefore, current technology is limited in terms of its capabilities and at least subject to the above limitations and deficiencies. Embodiments of the present invention provide systems and methods for overcoming difficulties in calibrating ESD detectors.

FIG. 1B shows a screenshot of a typical exemplary voltage / current waveform of a CDM electrostatic event in which discharge occurs in the form of a spark between two conductive parts. Top waveform 180 is an example output signal (current pulse) similar to the example output signal generated by the Charged Device Model Event Simulator (CDMES) as discussed below in accordance with an embodiment of the present invention. Bottom waveform 185 is an exemplary MicroESD antenna 135 in response to an incident propagating field.

In FIG. 1B, the top waveform 180 shows a pulse signal similar to a pulse signal that can also be generated and / or simulated from the CDMES device discussed below in accordance with an embodiment of the present invention. Bottom waveform 185 shows the radiated signal detected by antenna 135 coupled to minipulse detector 105. The minipulse detector 105 includes electronic circuitry capable of receiving a signal intercepted by the antenna 135. As will also be discussed below, if an electronic circuit determines that this signal is an ESD event of interest based on the ESD voltage and pulse duration threshold levels, the electronic circuit will classify the signal as an ESD event 110. .

In one embodiment of the invention, an apparatus for monitoring electrostatic discharge (ESD) events incorporating a charged device model event simulator (CDMES) unit comprises at least one positioned within a first process region. An antenna; And an ESD detector coupled to the at least one antenna, wherein the ESD detector is wirelessly coupled to the CDMES unit, and the ESD detector is calibrated for different discharge energy generated by the CDMES unit.

In another embodiment of the present invention, an electrostatic discharge (ESD) event monitoring method incorporating a charged device model event simulator (CDMES) unit comprises: detecting discharge energy; And calibrating the electrostatic detector for different discharge energies.

It is to be understood that the foregoing general description and the following detailed description are exemplary and explanatory only, and do not limit the invention as claimed.

The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate one (several) embodiment (s) of the invention and, together with the description, serve to explain the principles of the invention.

Non-limiting and non-exhaustive embodiments of the present invention are described with reference to the following figures, wherein like reference numerals refer to like parts throughout the various figures unless otherwise specified.
1A is a diagram of a typical discharge model of a charged (IC) device CDM event in a tool or processing chamber.
FIG. 1B is a screenshot of a waveform diagram of a typical exemplary voltage / current waveform of a CDM electrostatic event in which discharge occurs in the form of a spark between two conductive parts.
2 is a general diagram of a charged device model event simulator with an external high voltage power supply (HVPS) and scope, in accordance with an embodiment of the invention.
3A is a block diagram of a CDMES pulse waveform showing a typical current pulse generated when the CDMES is triggered in accordance with an embodiment of the present invention.
3B is a diagram of a system (or apparatus) that includes a charged device model event simulator, in accordance with an embodiment of the present invention, which system is configured to also provide a calibration method for an ESD event detector.
3C is a diagram of a system (or apparatus) according to another embodiment of the present invention.
4A is a diagram illustrating a general multi-antenna ESD detection array, in accordance with various embodiments of the present invention.
4B is a diagram illustrating a MicroESD antenna assembly, in accordance with various embodiments of the present invention.
5 is a block diagram of an ESD detector MiniPulse according to an embodiment of the present invention.
6 is a schematic diagram of an ESD monitor circuit of the ESD detector of FIG. 7 in accordance with an embodiment of the present invention.
7 is a general diagram of a minipulse ESD detector as seen from the outside, in one embodiment of the invention.
8 is a flowchart of a minipulse ESD calibration process in accordance with an embodiment of the present invention.

In the description herein, numerous specific details are provided, such as examples of components, materials, portions, structures and / or methods, to provide a thorough understanding of embodiments of the present invention. However, those skilled in the art will recognize that embodiments of the present invention may be practiced without one or more of the specific details or with other apparatus, systems, methods, components, materials, parts, structures, and the like. will be. In other instances, well known components, materials, portions, structures, methods or operations have not been shown or described in detail to avoid obscuring aspects of embodiments of the present invention. In addition, the figures are representative in nature, and the shapes are not intended to illustrate the precise shape or precise size of any element and are not intended to limit the scope of the invention.

Those skilled in the art will, in the drawings, refer to an element or portion as being "on" (or "connected", "coupled", or "attached" to) another element, such that the element or portion is directly on It will be appreciated that there may be (or may be attached directly to) or intervening elements may also be present. Also, "inner", "outer", "top", "above", "bottom", "bottom", "bottom", "bottom", "top", "toward", and "opposite" and similar terms Relative terms such as these may be used herein to describe the relationship of one element to another. It is to be understood that these terms are intended to encompass different orientations of the device, in addition to the orientation depicted in the figures.

Although the terms first, second, etc., are used herein to describe various elements, components, parts, regions, layers, chambers, and / or sections, these elements, components, portions, Regions, layers, chambers and / or sections should not be limited by these terms. These terms are only used to distinguish one element, component, part, region, layer, chamber or section from another element, component, portion, region, layer, chamber or section. Thus, the first element, component, portion, region, layer, chamber or section discussed below may be referred to as a second element, component, portion, region, layer, chamber or section without departing from the teachings of the present invention.

In addition, the elements illustrated in the figures are schematic in nature, the shapes of which are not intended to illustrate the precise shape of the elements of the device and are not intended to limit the scope of the invention. Also, based on the discussion of embodiments of the present invention as presented herein, the positions and / or configurations of the components in the figures may vary in different sizes, different shapes, different positions and / or different configurations. Those skilled in the art will recognize that it can. Therefore, the various components shown in the figures may be placed in different positions different from the configuration as shown in the figures. The components in the figures are illustrated in a non-limiting example position for the purpose of illustrating the functionality of embodiments of the present invention, and these components in the figures may be configured in other example positions.

In accordance with an embodiment of the present invention, a charged device model event monitoring system (or apparatus) is generally an echo chamber in which semiconductor tool processing chambers have a relatively high electrical noise level due to virtually surrounding metal case elements. Was developed in consideration of the

In practical aspects, each tool has its own characteristics (eg, EMI landscape) upon reflection of internal electromagnetic field radiation caused by an electrostatic discharge event. A typical scenario for a CDM event is that the charged IC device discharges when it contacts a tool or process element of a different electrical potential. This discharge through the dielectric gap (typically air) causes the dipoles formed by the different potentials to collapse, or the capacitors formed between the charged IC and tool components to collapse. Embodiments of the invention also provide an ESD event monitor, also referred to herein as a "minipulse" or minipulse detector or ESD detector. Monitors are, for example, low cost event monitors for workstations, electronics production tools, processes and mobile applications. The resulting radiation pulse electromagnetic waveform (radiation signal) is detected by, for example, a minipulse detector and an antenna communicatively coupled to the minipulse detector. If the detected field voltage level of this pulse waveform exceeds the threshold corrected by the Charged Device Model Event Simulator (CDMES) equipment, the minipulse detector registers a significant CDM event.

CDM events are characterized by a short (typically less than approximately 4 nanoseconds) duration change in the electromagnetic field, for example, and in the antenna, generates a high slew rate induced signal (current) rise signal. Therefore, with regard to tool ESD monitoring, the detection system used must distinguish the CDM signal of interest from the tool noise that is common in an echo chamber environment.

In accordance with various embodiments of the present invention, calibration methods for ESD detectors are provided. For example, suitable equipment, such as CDMES devices known in the art, can be used to simulate CDM events, and the calibration method is performed in accordance with embodiments of the present invention. For example, in situ monitoring of CDM events is facilitated by simulating a group of spark gap discharges in a real tool at the point where IC devices contact conductive tool elements. Disruptive charged capacitor discharge simulates a CDM event at a preselected voltage threshold for a given IC device. When this procedure is complete, the tool can be considered to be calibrated for IC CDM ESD event detection at the specified level.

Different types of CDMES devices known or to be developed in the future can be used to simulate CDM events, and a calibration method according to an embodiment of the invention is performed after simulating a CDM event or different discharge energy.

The CDMES is configured in some embodiments as a device having a moving electrode open in the discharge gap, or a device having a mercury or RF relay or a high voltage RF relay, for example a reed relay.

The CDM event simulated discharge produces signals that are intercepted and detected at the receiving antenna of the monitoring device (minipulse). A minipulse antenna (MicroESD) is coupled to the minipulse (see FIG. 3B) and allows the minipulse to receive waveforms due to an ESD event. Minipulses can be calibrated in-situ by varying the position of the minipulse antenna and / or the CDMES discharge voltage with respect to the expected CDM event source.

Therefore, CDMES is a charged device simulator that generates known radiated sparks that resemble the occurrence of discharge when a charged device approaches or contacts a socket. This CDMES is used to calibrate minipulses. The DC power supply is coupled to the CDMES and any suitable power supply voltage values (eg, 100V, 200V, 500V, or other values) are drawn into the CDMES. When the ESD event is simulated, the antenna detects the waveform from the CDMES-generated discharge and the minipulse captures and processes the waveform detected by the antenna. Examples of waveforms due to CDMES-generated discharges are observed in an oscilloscope, for example as shown in FIG. 1B, as further discussed below.

Based on the calibration plot and known product CDM fault thresholds, an ESD threshold voltage level can be set (or otherwise configured) for the minipulse detector. An output alarm signal from the minipulse can be generated and sent to the tool control system if the CDM event exceeds the threshold level for the actual IC discharge event in the tool.

The CDM event simulator is designed to allow the ESD monitor (detector) to be calibrated inside the tool and process where the CDM event occurs. This simulation device allows a calibrated CDM event of different voltage amplitudes to be generated at the point where the production device is most vulnerable and the ESD monitoring sensors are placed. This approach allows the highest level of handling safety for sensitive devices.

CDM Event Simulator (CDMES)

IC devices are usually characterized for fault thresholds in formal test benches and machines designed to simulate discharges on various device input and output connections. This information is used to assess risk at all stages of device manufacturing and system integration. In an embodiment of the invention, a method is provided by using an ESD event monitoring device and fault threshold information in conjunction with a CDM Event Simulator (CDMES).

For example, in many applications in semiconductors, disk-drives, FPDs, automated IC handling, and hosts of other fabrication processes, where direct discharge (electrostatic discharge between IC pins and grounded conductors) can occur Handle sensitive products (see for example FIGS. 1A and 1B).

Simulating CDM events at the point (or area) of monitoring presents challenges when attempting to use actual charged devices. Some of these difficulties are related to the repeatability of the discharge event itself. Other difficulties also exist due to the configuration of the process point itself and the conditions imposed on the electric field waveform emitted by the materials. Two versions of the CDM event simulator provide a repeatable CDM calibration event at a process point that takes into account uncharacterized location conditions (a general view of CDM event simulator version 1 is shown in FIG. 2).

The systems and methods discussed herein (with various CDMES and minipulse detectors) can be used in a tool or processing chamber and can be used in an open work bench, on any table, in a real environment, or in an ESD detector. It should also be noted that for calibration purposes the calibrated CDM may be used in any other suitable environment where it is radiated (created) and detected.

CDMES Version 1: Mechanical Gap for Generating CDM Events:

The first version of the CDM event simulator (CDMES) uses mechanical gap control to simulate a collapse capacitor event to simulate electrostatic discharge occurring between an object (target) and a charging IC at different potentials or ground references. In particular, this embodiment models a Charged Device Model (CDM) discharge type that features a fast single-peak pulse waveform of the moving current between the device and ground. CDMES power circuits contain high resistance (eg, approximately 100 mega ohms or more), so that the voltage across the gap is high (approximately 25V-3000V range), and the applied current is less than 10 microamps across this range. do.

Electrostatic discharges occur because of any charged contact and conventional ground contact (see FIGS. 1A and 1B). Therefore, when the CDMES is charged to the supply voltage, the CDMES will simulate an ESD event that generates a pulse waveform detectable by the oscilloscope and reproduced in the oscilloscope.

CDM pulses as reproduced on an oscilloscope are graphs of current pulse waveforms and correspond to the conventional CDM waveforms referenced in all standard documents (IEC 61000-4-2, ISO10605, JESD22-C101E). The generated waveform also corresponds to the input CDM pulse waveform that official device test machines (eg, see standard references above) use to evaluate device ESD sensitivity.

2 is a general diagram of a charged device model event simulator 200 having an external high voltage power supply (HVPS) 205 and a discharge head 202 electrically coupled to the scope 210.

3A is a typical CDMES pulse waveform showing the discharge current pulse generated when the CDMES is triggered. In this example of the oscilloscope screen shot 300, for example, a voltage discharge of approximately 100V from the HVPS 205 will trigger the CDMES to generate a typical current pulse 305 in waveform 310. This conventional current pulse 305 will cause an electrostatic event in which a discharge occurs in the form of a spark between two conductive parts.

3B is a diagram of a system 350 (or apparatus 350) that includes a charged device model event simulator 352 (or CDMES 352, or CDMES unit 352), in accordance with an embodiment of the present invention. The system 350 is also configured to provide a calibration method for the ESD event detector 355. Therefore, FIG. 3B shows a CDMES ESD calibration for minipulse ESD event detector 355. The ESD simulation and calibration method for the ESD event detector 355 performed by the CDMES 352 may be made (in-drilling) within the actual tool or processing chamber 362. Instead, however, as mentioned above, embodiments of the CDMES may be used in an open workbench, on any table, in the real environment, or in any other suitable environment in which a calibrated CD is created and detected for the purpose of calibrating the ESD detector. May be used.

As discussed similarly with reference to FIG. 2, CDMES 352 is coupled to (and operates with) HVPS 205 and scope 210. The CDMES 352 is electrically coupled via an electrical link 266 (eg, a cable) to a power source 205 that supplies voltage to the CDMES 352. The CDMES 352 is also connected via an electrical link 267 (eg, a cable) to an output signal (current pulse) generated by the CDMES device 352 as further discussed below (the output signal of FIG. 3A). (See 310) is electrically coupled to the oscilloscope 210 to detect and measure. When the trigger button is pressed, CDMES 352 (CDMES unit 352) uses the internal ESD event generation mechanism and the voltage from HVPS 205 to generate a current pulse event.

The discharge head (of CDMES 352) is charged by the voltage from HVPS 205. Antenna 382 (coupled to ESD detector 355) intercepts radiation 380 (or electromagnetic wave 380) of the discharge event generated within CDMES 352. Antenna 382 is configured to detect different discharge energies in radiation 380. As also mentioned above, simulation of an ESD event using CDMES 352 and corresponding elements (eg, HVPS 205, scope 210, and ESD detector 355) is performed in chamber 362. Or may be performed outside the chamber 362 (ie, on an open workbench, on any table, in the real environment, or on which a calibrated CDM is generated and detected for the purpose of calibrating the ESD detector 355 May be carried out in another suitable environment).

This figure of FIG. 3B shows the radiation 380 in the direction of the NULL field when the antenna 382 is along the axis of the radiating element (discharge head) of the CDMES 352 and is perpendicular to the element. Any signal will probably be due to reflection. If CDMES 352 is rotated approximately 90 degrees to CCW, the signal will be significantly affected.

CDMES 352 is discharged at the point where normal device handling occurs, simulating a device CDM discharge event. ESD event detector 355 (minipulse 355) has a relay output for notifying the tool control system of an ESD event.

The gate detection input of the ESD event detector 355 is a test point that can be utilized to set the ESD trigger threshold level of the minipulse 355, where the ESD trigger threshold level will distinguish the ESD event of interest.

The relay output of the ESD event detector 355 can be used to monitor the minipulse alarm condition (of the minipulse 355). The relay output is, for example, an open collector driver that is pulled to ground simultaneously with an audible alarm sound from minipulse 355.

During the process of calibrating the minipulse detector 355 (FIG. 3B), the collapse capacitor and various supply voltage values (e.g., approximately 20V, 100V, 500V or other values) of the CDMES 352 may be the user's preferred ESD event. Let's simulate the intensity.

 In an embodiment of the invention, this method of CDM calibration disclosed herein has a number of possible effects that may be one or more of the following.

Ability to calibrate ESD sensors in tools and processes (they will be used rather than just using experimental calibration or approximate approximation routines).

In-drilling CDM simulation taking into account variable conditions that automatically affect sensor calibration.

Allows statistical verification of ESD sensor validity through ease of high repetition event simulation.

Allow device handling tools to be calibrated for CDM discharge events during the tool development process.

Allow ESD detector periodic calibration in situ, eliminating the need to remove the detector from the tool or process for experimental calibration.

Key benefits of this version of CDMES include one or more of the following:

Allow use of smaller radiating antennas in more constrained tool space.

CD simulated events are less volatile due to the elimination of the manual trigger interface of the first version of CDMES (ie triggering is done with a separate timed switch).

ESD event detector

In many applications in the host of semiconductors, disk drives, FPDs, automated IC handling, and other manufacturing processes, it works with ESD sensitive products in locations that are difficult to directly monitor / control. In addition, due to its nature, most of these environments are saturated with EMI noise sources, ranging from HVDC supplies, electric motors, and actuators to broadband communication (RF) units. Detecting ESD events at specific points related to product handling can be a challenge.

The four main features of the novel ESD event detector are:

Pulse slew Control of ESD detection by rate and duration in the nanosecond range. The “minipulse” detector 355 (FIG. 3B) can distinguish between different pulse event types. Accordingly, the minipulse detector generates an effective ESD-type event from other EMI (electromagnetic interference or emission) pulse packet signals (e.g., signal emission from motors, switching devices, cellular phones, televisions, WiFi, environmental noise, etc.). You can decide and choose. Therefore, the minipulse detector 355 determines whether the ESD pulse event fits the selected pulse event threshold so that the minipulse detector 355 determines that the ESD pulse event is a CDM charged device model instead of a machine model and a human model. You can determine if you are inside. As is known to those skilled in the art, ESD events in the charged device model, machine model, and human model will differ in resistance factor, capacitance factor, and signature. Although the embodiment of the minipulse detector 355 does not actually indicate a difference between CDM, HBM and MM type ESD events, the minipulse detector 355 is based on the signal validity for the trigger threshold, Determine if it fits within the time buffer (ie, is eligible as a pulse).

2. Adjustable discharge energy threshold control. Due to electromagnetic field attenuation over distance, many broadband ESD events are filtered by adjusting voltage sensitivity thresholds (eg, thresholds of 1 volt, 100 volts, 500 volts, or other values) to match the local event amplitude. Can be.

3. The ESD detection method will now be described according to an embodiment of the present invention. ESD events generate electromagnetic pulses. This pulse is formally described as electromagnetic radiation flux density, which radiates outward in a spherical shape from the source, and the radiated energy decreases as the electromagnetic wave moves away from the source. Minipulse 355 samples this expanding electromagnetic field by interaction with a dipole antenna via inductive field coupling. The energy of the expanding electric field is coupled to the antenna generating a signal on the antenna cable. The minipulse detector unit 355 demodulates the incoming signal on the cable and decomposes the various frequencies into its power components. Minipulse 355 measures the power to determine if the combined power (watts) of the radiated pulse transient is greater than the set of detection thresholds. If large, minipulse 355 triggers the event of interest. If the power level is below the set threshold for detection, the event is ignored. Minipulse detector 355 also samples the incoming signal during the pulse duration using a comparator circuit (see comparator 508 of FIGS. 5 and 6) to determine if the pulse is eligible as a promising ESD event. If the pulse duration is within normal time interval boundaries for CDM and other ESD events (HBM and MM), the pulse triggers the detector. This detection method is different from standard time domain (large frequency domain) signal analysis. Time domain measurements, such as those made in high speed wide bandwidth oscilloscopes, typically extract peak voltage levels. Minipulse 355 operates more similarly to a spectrum analyzer that extracts the power of an ESD event signal. The main advantage of this approach is economical detection hardware. The need for high speed sampling (such as in the time domain method) is not critical. Radiated pulse power across the signal frequency provides a very good first order approximation of the signal power, allowing comparisons between different ESD event amplitudes.

4. The "minipulse" energy threshold control sensitivity allows fine tuning down to very small acquisition areas. This is an important aspect of limiting the detected ESD event to only events of critical importance and / or events of user interest.

5. Antenna configuration. Another key factor in SD event detection for a particular process point is the shape and placement of the antenna 382 (FIG. 3B). The physical gain characteristics of the antenna 382 play an important role in controlling the ESD signal acquisition. The directional gain feature of a specially designed antenna (coupled to minipulse detector 355) can be used to calibrate minipulse detector 355 for given ESD events of user interest.

6. Antenna performance and noise Insensitivity . MicroESD antenna 382 (or micro antenna 382) is specifically designed for detecting electrostatic discharge (ESD) events. By engineering, ESD radiation energy can be detected directionally with respect to the source location while ignoring other proximity events of no interest.

Specific improvements of embodiments of the present invention to the prior art (US Pat. No. 6,563,316 and patent application US2009 / 0167313) and other available ESD event monitoring products are as follows:

1. Demodulation log amplifier 505 (FIG. 5) extracts multi-frequency amplification levels from the detected ESD signal. This “minipulse” 355 can more accurately distinguish signal levels for threshold control. Therefore, embodiments of the present invention provide a demodulated log amplifier 505 that operates in a measurement mode and generates an output signal that matches a selected threshold to distinguish signal levels. This technology is not used by other detector products on the market.

2. Antennas 382 ("MicroESD" antennas 382) specifically designed for use with this product utilize engineering gain characteristics for optimal detection in the specified range while excluding unwanted signal sources. The antenna's physical dimensions and structure are bandwidth optimized for electromagnetic discharge (ESD) radiation pulse transient signals. Other detectors on the market use standard multipurpose RF antennas with unnecessary broadband characteristics. This approach with on-the-fly detectors makes signal separation between ESD pulse transient events and other signal sources a major problem.

3. An in-drilling ESD monitor calibration method for detecting certain types of ESD events is now possible. Therefore, embodiments of the present invention may be deployed in tools and applications (or other specific areas) to detect specific pulse events and exclude other signals of interest. In contrast, current ESD event detectors are generally designed to detect ESD events without the above-mentioned advantages of embodiments of the present invention.

3C is a diagram of a system (or apparatus) 388 in accordance with another embodiment of the present invention. System 388 is shown in top plan view for clarity of discussion. As discussed similarly with respect to system 350 of FIG. 3A, system 388 is configured for electrostatic discharge (ESD) event monitoring and includes a charged device model event simulator (CDMES) unit.

In an embodiment of the present invention, system 388 includes at least one antenna 382a positioned within process region 389a and an ESD detector 355 coupled to antenna 382a. Because the antenna 382a is configured to receive radiation 380 from the CDMES unit 352, the antenna 382a is wirelessly coupled to the CDMES unit 352. ESD detector 355 is calibrated for different discharge energies generated by CDMES unit 352.

The process area 389a may be, for example, a tool process area or an area outside the tool process area.

In another embodiment of the invention, the process region (generally depicted as region 389) includes a first process region 389a and a second process region 389b. The first antenna 382a is positioned within the first process region 382a and the second antenna 382b is positioned within the second process region 389b.

In an embodiment of the invention, the first antenna 382a is coupled to the ESD detector 355 and the second antenna 382b is also coupled to the ESD detector 355. In another embodiment of the present invention, the second antenna 382b is coupled to another ESD detector 356 and not to the ESD detector 355.

Typically, the first process region 389a is separated from the second process region 389b by a distance 391, and the first antenna 382a and the second antenna 382b form multi-channels. The distance 391 is adjustable.

In one embodiment, the first antenna 382a and the second antenna 382b may have similar antenna response sensitivity. In another embodiment, the first antenna 382a and the second antenna 382b have different antenna response sensitivity.

Process regions 389 may differ in number from one or more process regions. Therefore, more than two process regions may be included in the system 388.

At least one of the process regions 389 may include a socket 373 (FIG. 3B) configured to receive the semiconductor chip 125 (FIG. 1A), or may be configured to receive a plurality of semiconductor chips. It may include sockets 373.

At least one of the process regions 389 may include a tweezer 392 configured to receive the wafer 393 in another embodiment, as best identified by reference numeral 396. Of course, the tweezers 392 may be other types of wafer processing tools 392.

At least one of the process regions 389 (or wafer 393) may include a conductive trace 394 accessible by the test probe 395 in one embodiment, as best identified by reference number 397. Can be. Any of the process regions 389 may be another suitable type of region.

MicroESD antenna

Antennas used to detect ESD radiated pulse transients were typically standard antennas with very high gain. This makes detection of ESD events fairly easy, but makes it virtually impossible to determine the event origin. Because of this weakness, conventional antennas are rarely used to monitor critical processes.

The following references are also cited to provide additional background information related to antenna-related behaviors:

1. T.J. Maloney, Cover Title: "Easy Access to Pulsed Hertzian Dipole Fields Through Pole-Zero Treatment," IEEE EMC Society News, Summer 2011, pp.34-42.

2. T.J. Maloney, "Antenna Response to CDM E-fields", 2012 E0S / ESD Symposium, September 2012, pp. 269-278.

3. T.J. Maloney, "Pulsed Hertzian Dipole Radiation and Electrostatic discharge Events in Manufacturing" 2013 IEEE Electromagnetic Compatibility Magazine, Vol. 2, Quarter 3, pages 49-57.

A “microESD” antenna 382 (eg, antenna 382 coupled to minipulse detector 355 of FIG. 3B) was developed solely for the purpose of detecting ESD events in the vicinity of its source. The microESD antenna 382 has the exemplary ESD near field radiation pulse reception, while rejecting other near and far field pulse signatures due to the engineering directional gain characteristic of the example antennas 405, 410, 415, of FIG. 4A. 420, and / or 425 are realized with various versions of designed microstrip antennas. This allows the microESD antenna to perform well if other antennas do not identify a localized ESD event of interest.

In addition, the designed characteristics of these antennas allow for a very wide signal discrimination range (10-3000 V), which is not equivalent to the common antennas commonly used in ESD detection due to the saturation effect. When used with attenuators, very large ESD events can be effectively captured.

The ESD event should preferably be monitored as close as possible to its expected source. Typical monitoring distances for antenna installations range from, for example, approximately 1 "(2.54 cm) to approximately 6" (15 cm), although other distances may be acceptable. The microESD antenna 382 will intentionally be less efficient as it is farther away from the source due to signal amplitude reduction and detection threshold settings.

In FIG. 4A, multiple antenna configurations according to various embodiments of the present invention are disclosed. Minipulse 355 may be used with multiple coexisting antennas to detect ESD signals at different locations, simultaneously or separately. The same ESD signal sampling method is used, the only difference being the multiple antenna feed points 430. Feed points 430 are communicatively coupled to minipulse detector 355. Due to the low resistance loss and line propagation ESD transients of the antenna cable, signal degradation is minor for the purposes of detection and amplitude discrimination.

Multiple antennas can be deployed in arrays of dipole structures in almost any configuration. In FIG. 4A, five antennas 405-425 are shown. However, the array of dual poles configured in FIG. 4A may have more than five antennas or fewer than five antennas.

4B is a diagram illustrating a microESD antenna assembly 450, in accordance with an embodiment of the present invention. Assembly 450 includes a microESD antenna 455 coupled to an electrical link 460 (eg, cable 460) that is removably connected to ESD detector 355 (FIG. 3B).

Minipulse Circuit Description:

Reference is now made to the block diagram of FIG. 5 and the circuit diagram of FIG. 6. 5 is a block diagram of an ESD detector 500 (minipulse 500) in accordance with an embodiment of the present invention. 6 is a schematic diagram of the ESD monitor circuit 600 in the ESD detector 500 of FIG. 5, in accordance with an embodiment of the present invention. Minipulse 500 is also shown (and described) as ESD detector 355 in FIG. 3B.

The minipulse 500 uses a two-dimensional algorithm by EMI event analysis and threshold discrimination in the time domain to detect pulsed electrostatic discharge of constant electromagnetic energy. Using antenna configuration and antenna placement specific to the monitored object, minipulse 500 can provide ESD event detection for wider area coverage or for specific small areas of interest.

The ESD event signal 501 is detected by an antenna 502 that is connected to a shielded cable and attached to an input connector (eg, input SMA connector, J1). Signal 501 is an input filter / integrator 503 tuned to pass distorted frequencies (> 100 MHz) specific to a true ESD event and reject signals outside its range (e.g., sixth order high pass filter). Is processed by The filtered signal 501 (from filter / integrator 503) is then passed to a log-amplifier 505 (U2) which is a very fast six stage demodulation log-amp (Analog Devices AD8310). The output signal 506 of the log-amplifier (output signal 506 of U2) is inverted in that the quiescent voltage (no input signal) is approximately 2.5V. The circuit filtered incoming signal 506 is distinguished by power, duration and amplitude.

The stronger the input ESD event signal strength, the lower the output voltage 506 of the log-amplifier (output voltage 506 of U2). Typically this signal 506 will be in a range between approximately 2.5 and approximately 1.0 volts. The output voltage 506 (output voltage 506 of U2) is then compared to a preset DC voltage 507 (TP_Comp 507) using an ultrafast comparator 508 (U3) (Analog Devices AD8561).

Since output voltage 506 (output voltage 506 of U2) is compressed to about 1.5 volts swing, TP_Comp 507 uses a separate circuit (level setting block 510 of FIG. 5) to provide an easily configurable alarm level. Developed by)). The maximum TP_Comp voltage 507 of ˜2.0 volts is set by the Q4 NPN voltage source and potentiometer R12 which can be checked at TP2. The minimum TP_Comp voltage 507 of ˜1.0 volts may be set by potentiometer R10 and checked at TP1. Potentiometer R13 may then be adjusted throughout its mechanical range to produce TP_Comp 507 between ˜2.0 volts and ˜1.0 volts, matching the output range of log-amplifier 505.

Negative true condition if U3, i.e., comparator (AD8561) 508 detects a signal that is below TP_Comp 507 (on "+" or positive input) (on "-" or negative input) Is soon exerted on the output of comparator 508. This pulse is then delivered to U4a and U4b, which are pairs of one-shot multi-vibrators. U4a will be clocked on and Q = true (assuming J input is true). When U4a 1-shot is reset (due to R11 * C13 timeout, approximately 250 nSec), the second 1-shot U4b will be set to Q = True only if the output of U3 returns high. The reason is that the output of U3 is a fairly fast single pulse. If the pulse is too long, for example> 500 nSec (which indicates that it is not an ESD event of interest), the pulse is ignored.

Therefore, U4b is set to Q = true only because the pulse is determined to be the ESD event of interest. The alarm condition is indicated by, for example, an open collector output triggered by an audible tone, a visual red LED and "on".

The following block diagram and schematic diagram of minipulse 500 (FIG. 5) illustrate its basic operating elements. Antenna 502, which may be attached remotely or directly via a coaxial or triaxial cable, detects EMI signals (eg, signal 501). The antenna 502 is of the same type as, for example, the antenna 382 (FIG. 3B). EMI signals are processed to detect only signals within the frequency range of interest. Since the preferred signals have a very large dynamic range, the log-amp 505 amplifies to produce a useful signal 506. Signal 506 is then communicated to fast comparator 508 and compared to a predetermined threshold voltage level 507. Signals above this threshold 507 are then passed to a discriminator 512 that ignores all but the signals that meet the time definition of the EMI pulse of interest. This discriminator / generator 512 determines if an EMI pulse is a valid event by examining the slope of the EMI pulse. When triggered, circuit 512 is capable of audible, visually (eg, via audio and / or visual indicators 515) and remotely EMI events via open collector output driver transistor 516. Generate a pulse 514 that is used to indicate. The alarm output driver 516 sends an output event occurrence signal to the tool or computer to indicate that an event has occurred that exceeds a predetermined threshold voltage level.

7 shows a general view of a minipulse ESD detector 355 that can be seen externally in one embodiment of the invention. However, ESD detector 355 may have a different type of configuration than that of FIG.

8 is a flowchart of a calibration method 800 and implementation for an ESD detector, in accordance with an embodiment of the present invention. It should be appreciated that the order of the steps of method 800 may vary and some specific steps may also be performed at the same time. At 801 of the calibration method 800, a formal experimental device CDM test is performed on randomly sampled candidate devices. At 802, a determination is made regarding critical manufacturing process points for monitoring the presence of an ESD event (eg, tester, handler). At 803, in the in-drill ESD event, the calibration process is performed via the CDM Event Simulator (CDMES). Examples of in-drill ESD event calibration processes have been described above with reference to device 350 of FIG. 3B. At 804, a continuous ESD monitoring protocol may be established in connection with the minipulse ESD detector to ensure quality compliance.

When the minipulse ESD detector 355 is calibrated for a particular device withstand voltage threshold, this voltage threshold may typically be set to a voltage level that is less than the actual voltage fault level of the device. For example, if the device has an actual voltage failure level of approximately 200 volts, the voltage threshold would be set below 200 volts, for example approximately 50% of the voltage failure level or approximately 100 volts. This approach prevents real damage from occurring in the device. Therefore, at 805, an allowable applied voltage threshold is determined for each device type tested.

At 808, a minimum statistical sample is applied for verifying pass / fail ESD event detection for each location. For example, about 20 or 30 shots, or other numbers of shots, are applied to obtain the correct calibration.

At 806, the ESD detector 355 (eg, minipulse detector) is calibrated for a specific device withstand voltage threshold. It should be appreciated that after blocks 803, 805, and / or 808 are performed, the procedure of block 806 may then be performed.

At 807, the calibration CDMES current pulse waveforms are identified using an oscilloscope to verify the accuracy of the calibration shot. However, the use of oscilloscopes can also be omitted during this step in the calibration process.

 The following discussion provides additional details regarding the order of the calibration process in one embodiment of the present invention:

1. Place the microESD antenna 382 of the minipulse monitor (ESD detector 355) substantially closest to the process point in the tool where the sensitive IC device is to be placed.

2. Connect the microESD antenna cable to the powered minipulse monitor (355).

3. Set the DC supply voltage for the CDMES to the required threshold voltage level (typically approximately 50% of the IC device fault threshold).

4. Position CDMES at selected designated process points for sensitive IC device monitoring applications.

5. Trigger the CDMES adjusting the minipulse detection threshold control until the required ESD event detection threshold for minipulse 355 is reached.

6. Generate a minimum statistical group of CDMES discharges (eg, 12-24) at IC device specific threshold voltages to verify minipulse detector performance.

7. Record successful calibration data in the form of CDMES DC voltage levels, the number of successful minipulse detections during the statistical sampling group, and the minipulse threshold setting via front panel test points by digital multi-meter.

It is also understood that other systems in accordance with an embodiment of the present invention may have other forms and may have other different components arranged in different ways or in different orientations.

Other variations and modifications of the embodiments and methods described above are possible in light of the teachings discussed herein.

Exemplary embodiments of the invention, including those described in the Abstract, are not intended to be exhaustive or to be limited to the precise forms disclosed. While specific embodiments and examples of the present invention are described herein for illustrative purposes, various equivalent modifications are possible within the scope of the present invention as those skilled in the art will recognize.

These modifications may be made to the invention in light of the above detailed description. The terms used in the following claims should not be construed to limit the invention to the specific embodiments disclosed in the specification and the claims. Rather, the scope of the invention will be fully determined by the following claims, which are interpreted in accordance with the established principles of claim interpretation.

Claims (20)

An apparatus for monitoring electrostatic discharge (ESD) events incorporating a charged device model event simulator (CDMES) unit,
ESD detector coupled to at least one antenna
Including,
The ESD detector is wirelessly coupled to the CDMES unit,
The ESD detector is calibrated for different discharge energy produced by the CDMES unit,
The ESD detector is configured to compare an adjustable threshold voltage level with a signal amplitude of an ESD radiation pulse received by the at least one antenna,
The ESD detector is configured to determine whether a pulse duration of the ESD radiation pulse is within upper and lower time interval boundaries of an ESD event when the signal amplitude of the ESD radiation pulse exceeds the adjustable threshold voltage level. ,
The ESD detector generates a signal indicative of electromagnetic interference or emission (EMI) which is an effective ESD-type event when the pulse duration of the ESD radiation pulse is within the upper and lower time interval boundaries. Configured to generate,
The ESD detector is:
In response to the signal amplitude of the ESD radiation pulse exceeding the adjustable threshold voltage level, a second signal for a duration corresponding to the upper time interval boundary of the ESD event, the second signal being the adjustable threshold voltage. A first circuit configured to output a representation of the signal amplitude of the ESD radiation pulse above a level; And
A third signal-the third signal is the adjustable threshold only when the signal amplitude of the ESD radiation pulse returns below the adjustable threshold voltage level while the first circuit outputs the second signal during the duration A second circuit configured to output the ESD radiation pulse above a voltage level, the ESD radiation pulse being within the time interval boundaries
To include, ESD event monitoring device. The method of claim 1,
The at least one antenna comprises a first antenna coupled to the ESD detector and a second antenna coupled to the ESD detector;
And wherein the first antenna is disposed within a first process region and the second antenna is disposed within a second process region. The method of claim 2,
And wherein the first process region is separate from the second process region, and wherein the first and second antennas form a multi-channel. The method of claim 2,
And wherein the first and second antennas have similar antenna response sensitivities. The method of claim 2,
And wherein the first and second antennas have different antenna response sensitivities. The method of claim 2,
The first process region comprises a tool process region having a socket configured to receive a semiconductor chip and an external processing region, the outer processing region being outside the tool process region, separated from the tool process region by a distance, and And an antenna disposed within the outer processing region and coupled to the ESD detector. The method of claim 2,
And the first process region comprises at least one socket configured to receive at least one semiconductor chip. The method of claim 1,
The ESD detector is configured to detect a radiated pulsed electromagnetic wave signal, to distinguish between different pulse event types, and to register a CDM event when a charged device model (CDM) event exceeds a calibrated threshold. An apparatus for monitoring an ESD event, comprising circuitry. The method of claim 1,
And the ESD detector is configured to distinguish between different pulse event types based on an adjustable pulse event threshold. The method of claim 1,
The ESD detector includes circuitry configured to use a two-dimensional algorithm by analyzing electromagnetic interference (EMI) events in the time domain and performing threshold discrimination to detect pulsed electrostatic discharges of constant electromagnetic energy. The device for monitoring the ESD event. The method of claim 8,
And the ESD detector is calibrated for a specific device withstand voltage threshold based on one or more simulations of the CDM event. The method of claim 1,
The at least one antenna is:
A micro antenna coupled to the ESD detector,
And the microantenna includes an antenna gain characteristic for optimal detection in a specified range while excluding unwanted signal sources. The method of claim 1,
The ESD detector is configured to send the ESD radiation pulse to the alarm output driver to allow an alarm output driver to send an output event occurrence signal to a tool or computer, or to send the ESD radiation pulse to an audio or visual indicator. And configured for ESD event monitoring. A method for monitoring electrostatic discharge (ESD) events incorporating a charged device model event simulator (CDMES) unit,
Calibrating the ESD detector for different discharge energies;
Detecting one of the discharge energy through at least one antenna and the ESD detector;
Comparing the adjustable threshold voltage level with the signal amplitude of the ESD radiation pulses received by the at least one antenna;
In response to the signal amplitude of the ESD radiation pulse exceeding the adjustable threshold voltage level, a second signal for the duration corresponding to the upper time interval boundary of the ESD event-the second signal sets the adjustable threshold voltage level. Expressing the signal amplitude of the ESD radiation pulse in excess, determining whether a pulse duration of the ESD radiation pulse is within upper and lower time interval boundaries of the ESD event; And
Electro-magnetic interference or emission which is an effective ESD-type event only when the signal amplitude of the ESD radiation pulse returns below the adjustable threshold voltage level while the second signal is output for the duration; Generating a third signal, the third signal representing the ESD radiation pulse exceeding the adjustable threshold voltage level, the ESD radiation pulse being within the time interval boundaries.
To include, the method for monitoring the ESD event. The method of claim 14,
The detecting step is:
Distinguishing between different pulse event types based on an adjustable pulse event threshold. The method of claim 14,
The detecting step is:
ESD event, comprising using a two-dimensional algorithm by analyzing electromagnetic interference (EMI) events in the time domain and performing threshold discrimination to detect pulsed electrostatic discharges of constant electromagnetic energy. Method for monitoring. The method of claim 14,
Prior to calibrating the ESD detector for different discharge energies, further comprising setting antenna gain characteristics for optimal detection in a specified range while excluding unwanted signal sources. . The method of claim 14,
And the CDMES unit is configured for in situ calibration and includes a collapse capacitor. The method of claim 14,
The step of detecting the discharge energy is:
Detecting the emitted pulsed electromagnetic wave signal,
The calibrating step includes: distinguishing between different pulse event types and registering a CDM event when a charged device model (CDM) event exceeds a calibrated threshold. Way.
delete

Images